Toxicity of siRNAs through MTT cell proliferation assay. Huh-7 cells were plated at the density of 2 × 104 in 96 well plates. After 24 h cells were treated with different concentrations of siRNAs and control consisted of solvent in which siRNAs dissolved. After 24 h incubation period add MTT solution to all wells and incubated for 3-4 h at 37°C. Viable cells convert MTT to purple formazan crystal. Added DMSO to dissolve the formazan crystals and read absorbance at 570 nm and 620 nm.